Pakistan Dam Project Phase II
Tarbela 5th -extension project.
After the success on the 4th tunnel, ACET was invited to cover all diving activities for the 5th extension project.
The Tarbela Dam was built with five original tunnels, with the first three dedicated to hydropower generation, and the remaining two slated for irrigation use. The fourth phase extension project uses the first of the two irrigation tunnels, while the fifth phase extension will use the second irrigation tunnel. Tarbela Dam’s primary use is electricity generation. The installed capacity of the 4,888 MW Tarbela hydroelectric power stations will increase to 6,298 MW after completion of the planned fifth Extension.
Tarbela Dam is well protected and surrounded by many armed military and Water and Power Distribution Authority guards, to gain access, numerous check points must be cleared and the team must be a part of an official convoy as a vast part of the journey is on military roads. 3 containers loaded with commercial diving equipment had to be shipped from resp. Singapore, Thailand and Sri Lanka to the port of Karachi, followed by a 10-day drive over rural roads to the Karakoram mountains of North Pakistan. Temperatures in the Indus valley can soar up to 45 degrees Celsius in summer and plummet to below freezing in winter, intertwined by heavy storms that come rolling down the Himalaya’s. These strong seasonal changes, linked with an excess of meltwater during summer, give for an extremely small window for diving, which usually happens in the winter months when temperatures drop below freezing as does the water coming from the glaciers.
All diving operations are executed from a purpose-built work island, suspended in the middle of the lake, positioned by a battery of DGPS steered winches. On-site, the ACET team operates a decompression chamber, wet bell with LARS, hot water supply for suits and mixed gas boosting facilities. Diving is done in hot water suits using KM37 helmets as well as closed circuit mixed gas rebreathers. All divers are connected to the surface via an umbilical, giving hot water, communication, video and access to the gas bank with an average of 900.000Litres of different gas mixes stored.
The 5th extension project entailed opening a 35-ton hatch which has been buried for 50 years under 7meters of mud. Locate and open the locks, attach lifting cables and secure the slotcover once opened. The second phase entailed divers descending inside the slot shaft to the bottom of the intake tunnel, Inspect insides of the tunnel and video the gate seals. Next the gates(stoplocks) are lowered and diversplace jacks and wedges in place to secure a seal. Finally, the slotcover is closed and the tunnel drained of water in order for construction to begin.
On 19th of July our divers managed to successfully shut down tunnel number 4 after its’ opening in 1978.
Acet divers have been working in Pakistan Hydropower for over 5 years on a seasonal basis, having logged over 1000 dives in the cold murky waters of the Indus river. The current 5th Extension project is expected to be finalized in 2021.